BOSTON — It’s estimated that more than three million Americans have glaucoma, the second-leading cause of blindness, according to the World Health Organization. Yet only half of those people are aware they have the disease, which can lead to major vision impairments if left untreated.

And despite Massachusetts’ reputation as a progressive leader in health care, it is the only state in the country where optometrists, who are able to screen all patients for glaucoma and eye infections, must refer patients to an ophthalmologist if any condition is detected.

This proposal is nothing new to Beacon Hill, where the Senate has passed similar legislation six times in previous years, only to see it fail in the House.

“I think there are a variety of reasons for this change,” Jones explained. “It is allowed in 49 other states, the District of Columbia, and the VA — every place in the U.S. except here.”

Jones said this legislation would increase accessibility and availability of care since optometrists outnumber ophthalmologists, creating more options and lower costs.

Students are graduating from optometry school and leaving Massachusetts to go to one of the 49 other states that allow optometrists to treat glaucoma, Jones said.

Ophthalmologists differ from optometrists in their levels of training. An ophthalmologist is a medical doctor or an osteopathic doctor who specializes in eye and vision care. An optometrist is an eye doctor who has earned his or her Doctor of Optometry degree, but did not attend medical school.

There are more than 1,500 optometrists in Massachusetts and only 325 ophthalmologists. Those in favor of changing the current law to allow optometrists to treat glaucoma and prescribe anti-infection medications argue that it will provide more access and choices for Massachusetts residents.

They also say it will save $20 million for MassHealth, the state’s Medicaid program, and decrease co-pays for other insurance plans since optometrists would no longer have to refer patients to ophthalmologists, saving the system $50 million overall.

A recent poll by Anderson Robbins Research showed that 86 percent of respondents said they would vote “yes” on a hypothetical ballot measure to allow optometrists to write prescriptions for eye drops and to treat glaucoma.

The survey also found 69 percent of respondents who regularly see an ophthalmologist were supportive of the measure, while only 14 percent of those polled felt that the change would put patients’ safety at risk.

“Our research shows voters believe that allowing optometrists to treat glaucoma — like they have been doing in other states for as much as 40 years — will increase consumer choice and convenience and allow patients to avoid high-priced specialists and hospitals with longer wait times,” Chris Anderson, president and co-founder of Anderson Robbins Research, said in a recent press release for the Massachusetts Society of Optometrists.

Although this proposed legislation showed to be popular among voters, ophthalmologists are pushing back.

“It’s appropriate optometrists are diagnosing glaucoma,” Dr. John Mandeville, president of the Massachusetts Society of Eye Physicians and Surgeons told the Boston Business Journal. “I think there is a risk when you say if you’re able to test and treat, you are less likely to refer a patient, or more inclined to over-treat.”

Mandeville said that the proposed legislation is not clear enough in saying exactly what optometrists can treat.

“This is allowed in 49 other states, so if there were bad outcomes it would have been changed,” Jones said.​ ​“This is not a social policy. This really goes far beyond partisan politics. This is about access and lowering costs.”